1. Field of the Invention
The present invention relates to a secondary battery including an insulating case that is made of a sealing material having low thermal deformation, excellent flame-retardation, and excellent electric insulation so as to be able to enhance reliability of the secondary battery. The insulating case is disposed between a cap assembly and an electrode assembly of the secondary battery.
2. Description of the Related Art
A secondary battery is a battery that can be charged and discharged several times or more. Such a secondary battery is classified into various kinds depending on core substances associated with the charge and discharge of the battery and its appearance. Recently, square type lithium secondary battery is most widely used.
A secondary battery can be reused by charging and discharging several tens times or more while having power feeding ability equal to or more than an existing manganese dry battery, thereby can be used in a variety of applications. To this end, the secondary battery should have a shape and a size adaptable to each application, and a square type secondary battery is an example.
The square type secondary battery uses a metallic can with a thin thickness and a relatively long length. The inside of the can is formed with a space for receiving an electrode assembly and an electrolyte, and the can is manufactured in a well-type container, only one side of which is open. The aperture of the can receiving the electrode assembly is sealed with a combination of an insulating case and a cap assembly.
The secondary battery, in which the inside of the can is provided with the electrode assembly configured of a positive electrode plate, a negative electrode plate, and a separator and the electrolyte, charges and discharges electricity by a chemical reaction therebetween. The breakage of a secondary battery often occurs due to an internal short circuit, overcharge, overdischarge, and so on. In particular, if the negative occurrence, such as a short circuit, overcharge, and overdischarge, continues for a certain time, the temperature of the secondary battery significantly rises, and in the worse case, the secondary battery may explode.
Moreover, if the negative occurrence described above continues, the electrode assembly, the insulating case, and the cap assembly received in the inside of the can may be frequently damaged. The damage of the parts located inside the can leads to deformation of the can in shape, physical property, and so on. As a result, the sealing condition of the can becomes weak so that the electrolyte may leak from the can, thereby leading to lose the function as a secondary battery.